Ferroelectric random access memory (FRAM) is a non-volatile memory which stores data by using two different polarization orientations of a ferroelectric domain (or referred to as “electric domain”) in an electric field as logic information (“0” or “1”), and can be also referred to as “ferroelectric memory”.
The storage medium layer of a ferroelectric memory is a ferroelectric thin film layer having a reversible (or “switchable”) ferroelectric domain. Currently, the fastest speed of reversing an electric domain that can be measured in a lab can reach up to 0.2 ns. In fact, it can be even faster. Usually, the reversing speed of electric domain determines the read-write time of the memory, a coercive voltage for electric domain reversing determines the read-write voltage of elements, and it will decrease almost in equal proportion to a reduction of the thickness of the thin film. Therefore, the ferroelectric memory has such advantages as fast speed of data reading, low drive voltage, high density of storage, etc, and has earned widespread attention and rapid development in recent years.
Currently, the ferroelectric memory can be mainly divided into two categories according to a basic mode of work or operation: a destructive readout (DRO) FRAM and a non-destructive readout (NDRO) ferroelectric memory.
The conventional non-destructive readout (NDRO) ferroelectric memory builds the storage unit using one transistor T and one ferroelectric capacitor C (i.e., 1T1C), and is based on charge-reading.
CN patent application No. 201510036256.X, entitled “Non-Destructive Readout Ferroelectric Memory as Well as Method of Preparing the Same and Method of Read/Writing the Same” and CN patent application No. 201510036586.1, entitled “Non-Destructive Readout Ferroelectric Memory as Well as Method of Preparing the Same and Method of Operating the Same” disclose another NDRO ferroelectric memory which realizes NDRO in a way of current reading (i.e., non-destructive current readout), and which has advantages of simple preparation, low cost and high storage density. Therefore, it has received a lot of attention in the industry.
However, such a non-destructive current readout ferroelectric memory has a relatively small read current. For example, at a pA order of magnitude, a stable read current disclosed in the above CN patents is also in a range of 100 to 1000 pA. A small read current will lead to problems of poor reading ability of data, slow speed of reading (of the order of millisecond to second), etc., which have significantly restricted a practical application of such a ferroelectric memory.